Formation of submarine basalts

• Applicant: Dr. Thilo Bissbort
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560533365

The project has two main objectives, which are: 1) Determination of cooling rates of submarine basaltic glasses: The aim of this objective is to quantify cooling rates of submarine basaltic glasses from the HSDP2 drilling project by applying enthalpy relaxation geospeedometry using novel fast differential scanning calorimetry (FDSC) combined with TEM. The very high heating and cooling rates of FDSC allow us to determine cooling rates of basaltic glasses that have a strong tendency to crystallize, which has led to a significant paucity of cooling rate data for these compositions in the past. The small sample size (tens to hundreds of ng) required for FDSC will allow us to reconstruct cooling rate gradients on a small scale, for example in rims of pillow basalts, providing us with new data to unravel the complex thermal history of these lithologies. These results will be placed in a spatial and textural context to assess for example the influence of the distance from interfaces. This will be compared with heat conduction models and experiments. In addition, cooling rates obtained from samples taken from different depths in the core will be used to determine overall differences in the thermal history of different stratigraphic sections. The effects of glass composition, water content, and redox state will also be investigated. 2) Crystallization dynamics in basaltic glasses: We will perform the first ever controlled heating and cooling experiments on basaltic glasses in using conventional DSC and FDSC in combination with Raman spectroscopy, FIB, and TEM to study the crystallization dynamics in basaltic glasses. This novel method will be used to address two major questions that are: (i) What is the critical cooling rate at which crystallization occurs and how much of the glass crystallizes as a function of rate. (ii) Are observations by others of liquid immiscibility and associated nanolite formation in submarine basalts unique to some locations (e.g., Fani Maoré magmas of the Mayotte) or are these universal processes occurring in other basaltic melts cooled at the right rate? This highlights that the combination of DSC and FDSC will be suitable to probe different heating and cooling rates and to perform a detailed study in the dynamics of involved processes. Together, the two parts of the project will provide new insights into the formation of submarine basalts.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1006: Infrastructure area - International Continental Scientific Drilling Program (ICDP)
• International Connection: Switzerland
• Cooperation Partner: Dr. Jürgen Schawe